Experimenting with the possibilities of CSS3 transformations and the timed element of them. No longer does a CSS rollover state simply mean a colour change, you now have movement that you can schedule.
Prior to this the options for this were basically Flash or Javascript, both of which had their own issues, especially for accessibility on slow connections, and a requirement for up to date software and bad degradation when that wasn’t present.
So anyway, you can now rotate, slide or rescale your objects using only good old CSS.
In the wrong hands this could take us down the road of scrolling marquees/animated gifs from the 90’s where everything would flash or whizz around. The timed element of this is only supported by the webkit browsers (Safari, Chrome, etc) at the moment, and the timings are disregarded by Firefox which makes the movement abrupt.
Here are some other helpful articles about HTML5 & CSS3:
the-art-of-web.com
net.tutsplus.com